CODEWITHSUNDEEP
javascriptarraysecmascript-6
jonask
jonask

Reputation: 748

Sort array of dates to nearest date

I have an array of different dates. Lets say
const arr = ['21. may', '01. jan', '05. feb', '07. jun', '20. dec']

I want the dates in order, of the date closest to the date today. So in this case (18. marts), the output should be const arr = ['21. may', '07. jun', '20. dec', '01. jan', '05. feb']

Is this even possible, when the year is not included?

Upvotes: 3

Views: 1134

Answers (3)

jo_va
jo_va

Reputation: 13963

If you want to order the dates by distance to today with passed dates (negative distances) appearing last, you can do this:

const arr = ['21. may', '01. jan', '05. feb', '07. jun', '20. dec'];

const today = new Date('2019/03/18'); // use new Date() for current day

arr.sort((a, b) => toDate(a) - toDate(b));

function toDate(str) {
  const monthNames = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec'];
  const [day, monthName] = str.split(/\.\s*/);
  const month = monthNames.indexOf(monthName.toLowerCase());
  const date = new Date(today.getFullYear(), month, +day);
  if (date < today) date.setFullYear(date.getFullYear() + 1);
  return date;
}

console.log(arr); // ["21. may", "07. jun", "20. dec", "01. jan", "05. feb"]

Upvotes: 4

Zac Delventhal
Zac Delventhal

Reputation: 4010

If you add the string '2019' onto the end of your date strings, JavaScript's Date constructor will parse it as being in this year. Once you have a bunch of Date objects, it's easy enough to sort your strings, and use findIndex to get the first one that is in the future:

const dates = ['21. may', '01. jan', '05. feb', '07. jun', '20. dec'];

const sorted = [...dates].sort((a, b) => new Date(a) - new Date(b));
const soonest = sorted.findIndex(date => new Date(`${date} 2019`) > new Date());

const soonestDates = [...sorted.slice(soonest), ...sorted.slice(0, soonest)];
console.log(soonestDates);  // ["21. may", "07. jun", "20. dec", "01. jan", "05. feb"]

Upvotes: 0

marsibarsi
marsibarsi

Reputation: 1073

If you are sure that there are no years in your dates data, you can try this:

function sortDateStrArrayFrom(dayAndMonth, array) {
    const dateFrom = new Date(dayAndMonth);

    const datesBefore = [];
    const datesEqual = [];
    const datesAfter = [];

    array.forEach(dateStr => {
        const date = new Date(dateStr);

        if (date < dateFrom) {
            datesBefore.push(dateStr);
        }

        if (date === dateFrom) {
            datesEqual.push(dateStr);
        }

        if (date > dateFrom) {
            datesAfter.push(dateStr);
        }
    })

    return [...datesEqual, ...datesAfter, ...datesBefore];
}

const arr = ['21. may', '01. jan', '05. feb', '07. jun', '20. dec'];

sortDateStrArrayFrom('18. mar', arr); // ["21. may", "07. jun", "20. dec", "01. jan", "05. feb"]

If you need, it can be modified with date as input param or setting the same year for every date to work regardless of the year

Upvotes: 0

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